Wear indicator



NOV. 3, 1953 w, BIELSTEm 2,657,909

WEAR INDICATOR Filed March 11, 1949 ATTORNEY.

Patented Nov. 3, 1953 WEAR INDICATOR Walter J. Bielstein, Houston, Tex.,assignor, by mesne assignments, to Standard Oil Development Company,Elizabeth, N. J a corporation of Delaware Application March 11, 1949,Serial No. 80,834

3 Claims.

This invention relates to a drill bit used for drilling boreholes intosubsurface formations. More particularly, this invention relates to adrill bit which, when it is worn by a pre-determined amount duringdrilling operations, will give a signal of such wear at the surface ofthe earth.

In the drilling of boreholes into subsurface formations by the rotarydrilling method, particularly in drilling boreholes for the productionof minerals, such as oil and gas, the drill bit attached to the end ofthe drill stem is subjected to conditions which cause rapid wear of thecutting edges of the bit blades. The blades of several bits areordinarily worn off in drilling such a well. Of course, when the bladesare worn off a particular bit, the drilling crew must pull the drillstem out of the hole and replace the worn bit with a new bit beforeresuming drilling operations. When conventional bits are employed insuch operations, no positive method is available for determining thepoint when the cutting blades of the drill bit are worn to such anextent as to require replacement of the bit; consequently, the selectionof the time when the drill bit should be removed from the hole is whollywithin the judgment of the drilling crew. As would be expected,conventional drill bits are sometimes removed from the hole before theblades have been worn to the point where the drill bit should really bereplaced. On the other hand, and perhaps more commonly, the drill stemis sometimes not withdrawn from the hole and the bit replaced until longafter the blades have been worn to such an extent that little or no holeis being made. As a matter of fact, drilling is sometimes continueduntil the bit blades have been completely worn off the bit body and thebit body itself damaged by wear.

Although excessive wear of the cutting edge of the bit blades is themost frequent reason for replacement of conventional drill bits, itsometimes happens that the bit should be replaced because it has becomeworn out of gauge. Here again the drilling crew has no positive means ofknowing when the bit has become so worn. A drill bit is said to be wornout of gauge when the reaming edges of the bit blades have been worn tosuch an extent that the diameter of the hole being made is smaller thanmay conveniently be tolerated. For example, the diameter of a holedrilled with a bit having worn reaming edges may not be suflicientlygreat to permit the free passage of a new unworn drill bit subsequentlyintroduced into the hole. When this condition exists, the bore-holewalls must be enlarged by reaming in a suitable manner as with a newbit. Not only does reaming consume time but it also entails the risk ofa stuck drill bit.

It is an object of this invention to provide a drill bit which, whenworn by a pre-determined amount, will cause a decrease in fluid pressurein the mud stream used with the drill string and thus give a signal tothe drilling crew indicating that the drill bit should be removedbecause of excessive Wear.

It is a further object to provide a drill bit, the body of which willnot be damaged during drilling operations and in which the constructionis such that repair of the used bit is convenient and simple.

The foregoing objects, as well as other advantages, are attained by thepresent invention as will be apparent from the following detaileddescription taken in connection with the accompanying drawing in whichFig. 1 is a front view, partly in cross-section, of a drill bitconstructed in accordance with the present invention; and

Fig. 2 is a side view of the embodiment shown in Fig. 1.

Referring to the drawing in which like numorals refer to like elementsthroughout, the embodiment shown comprises a bit consisting of a bodyIt) and blades II and I2. The body It may be affixed to the lower end ofa drill stem l3 by any suitable means, such as by threads, the saiddrill stem being of conventional design fluidly connectible with asource of drilling fluid under pressure. Body I!) is provided with ahollow internal portion M in fluid communication with drill stem l3 whendrill stem [3 is connected with body I9. Ducts l5 and i6, conventionallytermed eyes or water courses, fluidly connect the hollow internalportion M of body Ill with the outer surface of said body, the outerterminus of ducts l5 and I5 being above the upper edge of bit blades I Iand I2, respectively, and normally directed in front of the cuttingfaces I! and I8, respectively, of the said blades. Bit blades II and I2may be of any desired design and preferably are made of hard, tough,metallic materials. The reaming edges l9 and 2t of bit blades II and I2,respectively, are approximately parallel to each other and to thelongitudinal axis of body I 0. Cutting edges 2! and 22 of bit blades IIand 12, respectively, may be perpendicular to the axis of body I0 thoughthey may taper outwardly and downwardly as shown in the drawing. Thecutting face I! of bit blade II is disposed approximately from thecutting face [8 of 3 bit blade l2. Bit blades II and I2 may beincorporated into the lower end of body ID in any suitable manner andare normally afllxed to the said body by welding. The drawing shows adual-bladed bit for the sake of simplicity although it will beunderstood that the bit of my invention may have a greater number ofblades.

The structure heretofore described is conventional to ordinary dragbits. In accordance with the present invention, the aforedescribedstructure is modified by providing means for indicating the point atwhich the bit blades have been worn by a pre-determined amount duringdrilling operations. Accordingly, body I is provided with duct 23fluidly connecting hollow internal portion H of said body with theexterior surface of said body above bit blades II and I2. In thedrawing, duct 23 is shown as opening into the exterior surface of bodyIt} above bit blade l2 and to the rear of cutting face [8 thereof.Downwardly extending tube 24 is fluidly connected with duct 23 and isanixed to the external surface of body ID. The open lower end 24' oftube 24 is positioned at a point above the lowermost portion of body l0.Plug 25 is adapted to fit slidably into the open lower end 24' of tube24 and to sealably close said tube. Plug 25 is maintained insealing-tight relation within lower open end 24' of tube 24 by means ofrod 26 which is afilxed, as by tack-welding, at its lower end to a pointon the back side of blade l2, its upper end abutting against stopper 25for holdin the said stopper within the lower open end 24' of tube 24 influid-tight relation therewith. The lower end of rod 26 is spot-weldedto the back side of blade l2 at the point on blade 12 at which it isdesired that wear be indicated. If desired. the upper end of rod 26 maybe affixed to plug 25 or rod 26 may be made an integral part of plug 25.The lower end of rod 26 is positioned on blade l2 below the lowermostportion of body ID. The lower end of rod 26 may also be positioned inclose proximity to reaming edge 20 of'blade I2, as shown in the drawing.

While plug 25 may consist of any material which will sealably close thelower end of tube 24, I prefer to employ a resilient material such asnatural or synthetic rubber. The resilient material may be stiffened, ifdesired, as by means of integrally included metallic wires or rods.

The structure of my invention having hereinbefore been fully described,its mode of operation will now be briefly indicated. When bit blades Hand I2 have been worn during normal drilling operations to the point atwhich rod 26 is tack-welded to blade l2, the weld on the rod will alsobe worn off, thereby releasing the lower end of rod 26 from engagementwith bit blade l2. With rod 26 removed from its position holding plug 25in sealing relation within the lower end 24 of tube 24, plug 25 isforced out of the lower open end 24 of tube 24 by reason of the pressureexerted by the drilling fluid with internal hollow portion l4 of body I0and tube 24. With tube 24 open to the flow of drilling fluid thepressure in drill stern l3 drops and the speed of the mud pumpincreases, thus indicating to the drilling crew that the bit has becomeworn to the point at which replacement is required. If the lower end ofrod 26 is positioned adjacent the reaming edge 29 of blade 12 as shownin the drawing, excessive wear of the reaming edges I9 and 20 will alsoeventually wear off the spot-weld at the lower end of rod 26, thuscausing a sudden drop in drilling fluid pressure as indicated above.

It is obvious that various changes may be made in the devicehereinbefore illustrated and described without departing from the spiritof the invention or the scope of the annexed claims.

What I wish to claim as new and useful and desire to secure by LettersPatent is:

1. A drill bit comprising, in combination a hollow body releasablyconnectible with a drill stem to a source of drilling fluid underpressure and provided with cutter blades having a cutting face, the bodyhaving at least one first duct (or each blade connecting the interior ofsaid body with the exterior of said body above said cutter blade andahead of the cutting face of said blade, said body having at least onesecond duct fluidly connecting the interior of said body with theexterior of said body above a cutter blade and to the rear of thecutting face of said blade, a downwardly extending tube in fluidcommunication at its upper end with the outer terminus of said at leastone second duct, the lower portion of said downwardly extending tubebeing substantially vertically extending, a plug adapted to flt slidablyinto the lower end of said tube in fluid-tight relation therewith and arod member mechanically ailixed at its lower end to one of said bladesin the path of cutter blade wear and having its upper end abuttingagainst said plug for normal 1y maintaining said plug in fluid-tightrelation within the lower end of said tube.

2. A drill bit comprising, in combination, a hollow body releasablyconnectible with a drill stem to a source of drilling fluid underpressure and provided with cutter blades having a cutting face, the bodyhaving at least one first duct for each blade connecting the interior ofsaid body with the exterior of said body above said cutter blade andahead of the cutting face of said blade. said body having a second ductfluidly connecting the interior of said body with the exterior of saidbody above a cutter blade and to the rear of the cutting face of saidblade, a downwardly extending tube in fluid communication at its upperend with the outer terminus of said second duct and aflixed to the outersurface of said body, the lower portion of said tube being substantiallyvertically extending, the lower end of said tube terminating above thelowermost portion of said body, a removable plug adapted to fit slidablywithin the lower end of said tube in fluid-tight relation therewith, arod member welded at its lower end onto the back side of said blade, thewelded lower end of said rod being positioned below the lowermostportion of said body in the path of cutter blade wear, the upper end ofsaid rod member abutting against said removable plug normally tomaintain said plug in fluid-tight relation with said tube.

3. A device in accordance with claim 2 in which the removable plug isconstructed of rubber.

WALTER J. BIELSTEIN.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,296,183 Richard Sept. 15, 1942 2,461,164 Lewis a Feb. 8,1949 2,489,687 Thrift et al. Nov. 29, 1949 2,549,278 Yancey Apr. 17,1951 2,562,833 True July 31, 1951 FOREIGN PATENTS Number Country Date295,352 Great Britain Aug. 28, 1928

